This document establishes the requirements for the TActical COmmunications protocol 2 (TACO2), part of the National Imagery Transmission Format Standards (NITFS). National Imagery Transmission Format (NITF) is a standard format for transmitting digital imagery and imagery-related products among members of the Intelligence Community, and TACO2 is a protocol suite that may be used for that transmission. It includes requirements for Forward Error Correction (FEC), which is necessary to ensure interoperability and to promote commonality among subsystems that comply with NITFS.

This standard establishes the requirements to be met by systems complying with NITFS when using the TACO2 protocol, and defines the protocols and formats that make up TACO2. All aspects of TACO2 that affect functional interoperability are specified herein. In addition, guidance is provided for those aspects of TACO2 operation that are not strictly related to interoperability but may affect technical performance or resistance to error.

This standard is applicable to the Intelligence Community and the DOD. It is mandatory for all Secondary Imagery Dissemination Systems (SIDS) in accordance with the memorandum by the Assistant Secretary of Defense for Command, Control, Communications, and Intelligence ASD(C3I), Subject: National Imagery Transmission Format Standards (NITFS), 12 August 1991. This directive shall be implemented in accordance with JTEO Circular 9008, and MIL-HDBK-1300. New equipment and systems, those undergoing major modification, or those capable of rehabilitation shall conform to this standard.

TACO2 is designed as a single protocol stack that provides for message transfer over a wide variety of tactical communication circuits. It is particularly appropriate for use over circuits where other protocol suites operate poorly or not at all, but also is designed to perform well over any communications circuit. It can transfer any form of data, since it does not use any internal component of an NITFS message. It can be configured to operate over circuits not anticipated at initial installation; therefore, a conforming TACO2 implementation must implement all capabilities specified herein, except as specifically noted. The possible ranges of various parameters may be limited for specific applications; mandatory ranges are specified in this document. Additional information on NITFS compliance is available in JIEO Circular 9008.

As a minimum, only those features or functions specified herein, necessary to ensure interoperability among systems, shall be implemented in an equipment item. While every effort has been made to include all the features necessary, certain aspects depend on system application and must be tailored by the specification writer. These aspects include:

a. User choice of appropriate FEC selection.

b. Automatic switching of FEC code based on the conditions of the tactical line.